Discovery and Structure−Activity Relationship of (1R)-8-Chloro-2,3,4,5-tetrahydro-1-methyl-1H-3-benzazepine (Lorcaserin), a Selective Serotonin 5-HT2C Receptor Agonist for the Treatment of Obesity

Seven-membered N-heterocycles as approved drugs and promising leads in medicinal chemistry as well as the metal-free domino access to their scaffolds

Azepanes or azepines are structural motifs of many drugs, drug candidates and evaluated lead compounds. Even though compounds having N-heterocyclic 7-membered rings are often found in nature (e.g. alkaloids), the natural compounds of this group are rather rare as approved therapeutics. Thus, recently studied and approved azepane or azepine-congeners predominantly consist of semi-synthetically or synthetically-obtained scaffolds. In this review a comparison of approved drugs and recently investigated leads was proposed taking into regard their structural aspects (stereochemistry), biological activities, pharmacokinetic properties and confirmed molecular targets. The 7-membered N-heterocycles reveal a wide range of biological activities, not only against CNS diseases, but also as e.g. antibacterial, anticancer, antiviral, antiparasitic and against allergy agents. As most of the approved or investigated potential drugs or lead structures, belonging to 7-membered N-heterocycles, are synthetic scaffolds, this report also reveals different and efficient metal-free cascade approaches useful to synthesize both simple azepane or azepine-containing congeners and those of oligocyclic structures. Stereochemistry of azepane/azepine fused systems, in view of biological data and binding with the targets, is discussed. Apart from the approved drugs, we compare advances in SAR studies of 7-membered N-heterocycles (mainly from 2018 to 2023), whereas the related synthetic part concerning various domino strategies is focused on the last ten years.

Using artificial intelligence to identify drugs for repurposing to treat l-DOPA-induced dyskinesia

Repurposing regulatory agency-approved molecules, with proven safety in humans, is an attractive option for developing new treatments for disease. We identified and assessed the efficacy of 3 drugs predicted by an in silico screen as having the potential to treat l-DOPA-induced dyskinesia (LID) in Parkinson's disease. We analysed ∼1.3 million Medline abstracts using natural language processing and ranked 3539 existing drugs based on predicted ability to reduce LID. 3 drugs from the top 5% of the 3539 candidates; lorcaserin, acamprosate and ganaxolone, were prioritized for preclinical testing based on i) having a novel mechanism of action, ii) having not been previously validated for the treatment of LID, iii) being blood-brain-barrier penetrant and orally bioavailable and iv) being clinical trial ready. We assessed the efficacy of acamprosate, ganaxolone and lorcaserin in a rodent model of l-DOPA-induced hyperactivity, with lorcaserin affording a 58% reduction in rotational asymmetry (P < 0.05) compared to vehicle. Acamprosate and ganaxolone failed to demonstrate efficacy. Lorcaserin, a 5HT2C agonist, was then further tested in MPTP lesioned dyskinetic macaques where it afforded an 82% reduction in LID (P < 0.05), unfortunately accompanied by a significant increase in parkinsonian disability. In conclusion, although our data do not support the repurposing of lorcaserin, acamprosate or ganaxolone per se for LID, we demonstrate value of an in silico approach to identify candidate molecules which, in combination with an in vivo screen, can facilitate clinical development decisions. The present study adds to a growing literature in support of this paradigm shifting approach in the repurposing pipeline.

Calcium and Neural Stem Cell Proliferation

Intracellular calcium plays a pivotal role in central nervous system (CNS) development by regulating various processes such as cell proliferation, migration, differentiation, and maturation. However, understanding the involvement of calcium (Ca2+) in these processes during CNS development is challenging due to the dynamic nature of this cation and the evolving cell populations during development. While Ca2+ transient patterns have been observed in specific cell processes and molecules responsible for Ca2+ homeostasis have been identified in excitable and non-excitable cells, further research into Ca2+ dynamics and the underlying mechanisms in neural stem cells (NSCs) is required. This review focuses on molecules involved in Ca2+ entrance expressed in NSCs in vivo and in vitro, which are crucial for Ca2+ dynamics and signaling. It also discusses how these molecules might play a key role in balancing cell proliferation for self-renewal or promoting differentiation. These processes are finely regulated in a time-dependent manner throughout brain development, influenced by extrinsic and intrinsic factors that directly or indirectly modulate Ca2+ dynamics. Furthermore, this review addresses the potential implications of understanding Ca2+ dynamics in NSCs for treating neurological disorders. Despite significant progress in this field, unraveling the elements contributing to Ca2+ intracellular dynamics in cell proliferation remains a challenging puzzle that requires further investigation.

Enantioselective Synthesis of Biphenyl-Bridged ϵ-Sultams by Organocatalytic Mannich Reactions of Cyclic N-Sulfonylimines with Unactivated Ketones

A highly enantioselective Mannich reaction of biphenyl-bridged seven-membered cyclic N-sulfonylimines with methyl alkyl ketones is disclosed in this study. The reaction was performed under organocatalysis by using a quinine-derived primary amine as the catalyst in combination with a Brønsted acid as the co-catalyst. High yields (up to 89 %) and excellent enantioselectivities (up to 97 % ee) were observed. For methyl alkyl ketones containing a larger alkyl substituent, specific regioselective addition to the C=N bond is favored at the methyl group. On the contrary, ketones containing a smaller alkyl substituent or hydroxyacetone substrates gave major syn selective Mannich products at the methylene group.

Lorcaserin: Worthy of Further Insights? Results from Recent Research

Lorcaserin is a 3-benzazepine that binds 5-HT2C serotonin receptors in the hypothalamus, where it mediates lack of hunger and/or satiety, and in the ventral tegmental area, the site of origin of the mesolimbic and mesocortical dopaminergic projections, which mediate pleasure and reward. The drug has been first developed for the treatment of obesity, where it has shown efficacy, and subsequently trialed to counter substance use (mostly cocaine, cannabis, opioids, and nicotine) and craving, but showed inconsistent effects. Since 2020, the US Food and Drug Administration obtained that the drug was voluntarily withdrawn from the US market on the grounds that its long-term use was found to be associated with a greater incidence of some types of cancer. Provided it can show to be free from cancerogenic effects, ongoing research suggests that lorcaserin may have therapeutic potential for a variety of disorders and conditions beyond obesity. Since 5-HT2C receptors are involved in many diversified physiological functions (mood, feeding, reproductive behavior, neuronal processes related to impulsiveness, and modulating reward-related mechanisms) this drug has the potential to treat different central nervous system conditions, such as depression and schizophrenia.

NU-1223, a simplified analog of alstonine, with 5-HT2cR agonist-like activity, rescues memory deficit and positive and negative symptoms in subchronic phencyclidine mouse model of schizophrenia

The serotonin (5-HT)2 C receptor(R) is a widely distributed G-protein-coupled receptor, expressed abundantly in the central nervous system. Alstonine is a natural product that has significant properties of atypical antipsychotic drugs (AAPDs), in part attributed to 5-HT2 CR agonism. Based on alstonine, we developed NU-1223, a simplified β carboline analog of alstonine, which shows efficacies comparable to alstonine and to other 5-HT2 CR agonists, Ro-60-0175 and lorcaserin. The 5-HT2 CR antagonism of some APDs, including olanzapine, contributes to weight gain, a major side effect which limits its tolerability, while the 5-HT2 CR agonists and/or modulators, may minimize weight gain. We used the well-established rodent subchronic phencyclidine (PCP) model to test the efficacy of NU-1223 on episodic memory, using novel object recognition (NOR) task, positive (locomotor activity), and negative symptoms (social interaction) of schizophrenia (SCH). We found that NU-1223 produced both transient and prolonged rescue of the subchronic PCP-induced deficits in NOR and SI. Further, NU-1223, but not Ro-60-0175, blocked PCP and amphetamine (AMPH)-induced increase in LMA in subchronic PCP mice. These transient efficacies in LMA were blocked by the 5-HT2 CR antagonist, SB242084. Sub-chronic NU-1223 treatment rescued NOR and SI deficits in subchronic PCP mice for at least 39 days after 3 days injection. Chronic treatment with NU-1223, ip, twice a day for 21 days, did not increase average body weight vs olanzapine. These findings clearly indicate NU-1223 as a class of small molecules with a possible 5-HT2 CR-agonist-like mechanism of action, attributing to its efficacy. Additional in-depth receptor mechanistic studies are warranted, as this small molecule, both transiently and chronically rescued PCP-induced deficits. Furthermore, NU-1223 did not induce weight gain post long-term administrations vs AAPDs such as olanzapine, making NU-1223 a putative therapeutic compound for SCH.

5-HT2C Receptor Stimulation in Obesity Treatment: Orthosteric Agonists vs. Allosteric Modulators

Obesity is a substantial health and economic issue, and serotonin (5-hydroxytryptamine, 5-HT) is an important neurotransmitter system involved in the regulation of body weight. The 5-HT2C receptors (5-HT2CRs), one of 16 of the 5-HT receptor (5-HTRs) subtypes, play a significant role in food intake and body weight control. In this review, we focused on the 5-HTR agonists, such as fenfluramines, sibutramine, and lorcaserin, which act directly or indirectly at 5-HT2CRs and have been introduced into the clinic as antiobesity medications. Due to their unwanted effects, they were withdrawn from the market. The 5-HT2CR positive allosteric modulators (PAMs) can be potentially safer active drugs than 5-HT2CR agonists. However, more in vivo validation of PAMs is required to fully determine if these drugs will be effective in obesity prevention and antiobesity pharmacology treatment. Methodology strategy: This review focuses on the role of 5-HT2CR agonism in obesity treatment, such as food intake regulation and weight gain. The literature was reviewed according to the review topic. We searched the PubMed and Scopus databases and Multidisciplinary Digital Publishing Institute open-access scientific journals using the following keyword search strategy depending on the chapter phrases: (1) “5-HT2C receptor” AND “food intake”, and (2) “5-HT2C receptor” AND “obesity” AND “respective agonists”, and (3) “5-HT2C receptor” AND “PAM”. We included preclinical studies (only present the weight loss effects) and double-blind, placebo-controlled, randomized clinical trials published since the 1975s (mostly related to antiobesity treatment), and excluded the pay-walled articles. After the search process, the authors selected, carefully screened, and reviewed appropriate papers. In total, 136 articles were included in this review.

Relay Zn(ii)- and Au(i)-catalyzed aziridination/cyclization/ring expansion sequence to form 3-benzazepine derivatives

The synthesis of 3H-benzo[d]azepine-2-carboxylates from 2-alkynylphenyl aldimines and α-diazo esters using Zn(ii) and Au(i) catalysts is described.

Ni/Photoredox-Catalyzed C(sp3)-C(sp3) Coupling between Aziridines and Acetals as Alcohol-Derived Alkyl Radical Precursors

Aziridines are readily available C(sp³) precursors that afford valuable β-functionalized amines upon ring opening. In this article, we report a Ni/photoredox methodology for C(sp³)-C(sp³) cross-coupling between aziridines and methyl/1°/2° aliphatic alcohols activated as benzaldehyde dialkyl acetals. Orthogonal activation modes of each alkyl coupling partner facilitate cross-selectivity in the C(sp³)-C(sp³) bond-forming reaction: the benzaldehyde dialkyl acetal is activated via hydrogen atom abstraction and β-scission via a bromine radical (generated in situ from single-electron oxidation of bromide), whereas the aziridine is activated at the Ni center via reduction. We demonstrate that an Ni(II) azametallacycle, conventionally proposed in aziridine cross-coupling, is not an intermediate in the productive cross-coupling. Rather, stoichiometric organometallic and linear free energy relationship studies indicate that aziridine activation proceeds via Ni(I) oxidative addition, a previously unexplored elementary step.

Synthesis of Chiral Tetrahydro-3-benzazepine Motifs by Iridium-Catalyzed Asymmetric Hydrogenation of Cyclic Ene-carbamates

A highly efficient N,P-ligated iridium complex is presented for the simple preparation of chiral tetrahydro-3-benzazepine motifs by catalytic asymmetric hydrogenation. Substrates bearing both 1-aryl and 1-alkyl substituents were smoothly converted to the corresponding hydrogenated product with excellent enantioselectivity (91-99% ee) and in isolated yield (92-99%). The synthetic value of this transformation was demonstrated by a gram-scale hydrogenation and application in the syntheses of trepipam and fenoldopam.

Lorcaserin for Dravet Syndrome: A Potential Advance Over Fenfluramine?

Lorcaserin, a selective serotonin 5-HT_2C receptor agonist, was developed as an appetite suppressant with the rationale of minimizing the risk of cardiovascular toxicity associated with non-selective serotoninergic agents such as fenfluramine. Eight years after FDA approval, however, it was withdrawn from the market, when a large safety study suggested a potential cancer risk. Following in the fenfluramine footsteps and utilizing the repurposing approach coupled with the regulatory orphan drug designation, lorcaserin is currently in clinical development for the treatment of epilepsy. This potential novel indication builds on the evidence that 5-HT_2C receptor stimulation can protect against seizures, and accounts at least in part for fenfluramine's antiseizure effects in Dravet syndrome models. In animal models, lorcaserin shows a narrower range of antiseizure activity than fenfluramine. In particular, lorcaserin is inactive in classical acute seizure tests such as maximal electroshock and subcutaneous pentylenetetrazole in mice and rats, and the 6-Hz stimulation model in mice. However, it is active in the GAERS absence seizure model, and in mutant zebrafish models of Dravet syndrome. Preliminary uncontrolled studies in patients with Dravet syndrome have yielded promising results, and a phase III, double-blind, placebo-controlled, parallel group trial is currently ongoing to assess its efficacy and safety in children and adults with Dravet syndrome.

A ring expansion strategy towards diverse azaheterocycles

The development of innovative strategies for the synthesis of N-heterocyclic compounds is an important topic in organic synthesis. Ring expansion methods to form large N-heterocycles often involve the cycloaddition of strained aza rings with π bonds. However, in some cases such strategies suffer from some limitations owing to the difficulties in controlling the regioselectivity and the accessibility of specific π-bond synthons. Here, we report the development of a general ring expansion strategy that involves a formal cross-dimerization between three-membered aza heterocycles and three- and four-membered-ring ketones through synergistic bimetallic catalysis. These formal cross-dimerizations of two different strained rings are efficient and scalable, and provide a straightforward and broadly applicable means of assembling diverse N-heterocycles, such as 3-benzazepinones, dihydropyridinones and uracils, which are versatile units in numerous drugs and biologically active compounds. Preliminary mechanistic studies revealed that the C-C bond of strained ring ketones is first cleaved by the Pd⁰ species during the reaction.

The 5-HT2C receptor as a therapeutic target for alcohol and methamphetamine use disorders: A pilot study in treatment-seeking individuals

Alcohol use disorder (AUD) and methamphetamine use disorder (MUD) are prevalent and have high adverse impacts on both the individual and society. Current treatment strategies for these disorders are ineffective at a population level. Lorcaserin, a 5‐HT_2C receptor agonist, has shown potential at reducing the symptoms of substance use disorder. This pilot study (initiated prior to market withdrawal) examined feasibility and safety of lorcaserin treatment in people undergoing residential detoxification and treatment for AUD and MUD. This was an open label pilot study of lorcaserin where participants (n = 10 AUD; n = 8 MUD) received 10‐mg lorcaserin daily for 4 days then twice daily for 1 month. Primary outcome measures included recruitment and retention rate, incidence of treatment‐emergent events, incidence of methamphetamine or alcohol withdrawal‐related events, heart rate, and blood pressure. Secondary measures included pharmacokinetic data and self‐reported alcohol or methamphetamine use, craving, and psychological distress. AUD participants were recruited faster and had a greater retention rate compared with MUD participants. Lorcaserin did not alter vital signs, was well tolerated, and had a similar pharmacokinetic profile to individuals with obesity. Lorcaserin reduced self‐reported alcohol and amphetamine‐type substance use and craving in AUD and MUD participants, respectively. Self‐reported psychological health also improved over the treatment period for all participants. Despite the pilot nature of this study, our data support the notion of 5‐HT_2C receptors as a therapeutic target for drug and alcohol abuse.

Novel (R)-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,n]naphthyridines as potent and selective agonists of the 5-HT2C receptor

A series of novel (R)-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,n]naphthyridines were identified as potent and selective agonists of the 5-HT_2C receptor. Optimizations performed on a previously reported series of racemic tetrahydroquinoline-based tricyclic amines, delivered an advanced drug lead, (R)-4-(3,3,3-trifluoropropyl)-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,8]naphthyridine, which displayed excellent in vitro and in vivo pharmacological profiles.

Synthesis and biological evaluation of novel antipsychotic trans-4-(2-(1,2,4,5-tetrahydro-3H-benzo[d]azepin-3-yl)ethyl)cyclohexan-1-amine derivatives targeting dopamine/serotonin receptor subtypes

In this study, a series of trans-4-(2-(1,2,4,5-tetrahydro-3H-benzo[d]azepin-3-yl)ethyl)cyclohexan-1-amine derivatives as potential antipsychotics were synthesized and biologically evaluated to discover potential antipsychotics with good drug target selectivity. The preliminary structure-activity relationship was discussed, and optimal compound 12a showed both nanomolar affinity for D₂/D₃/5-HT_1A/5-HT_2A receptors and weak α₁ and H₁ receptor binding affinity. In addition, 12a was metabolically stable in vitro, displayed micromolar affinity for the hERG channel, and exhibited antipsychotic efficacy in the animal model of locomotor-stimulating effects of phencyclidine.

Design of oxa-spirocyclic PHOX ligands for the asymmetric synthesis of lorcaserin via iridium-catalyzed asymmetric hydrogenation

Phosphine-oxazoline (PHOX) ligands are a very important class of privileged ligands in asymmetric catalysis. A series of highly rigid oxa-spiro phosphine-oxazoline (O-SIPHOX) ligands based on O-SPINOL was synthesized efficiently, and their iridium complexes were synthesized by coordination of the O-SIPHOX ligands to [Ir(cod)Cl]₂ in the presence of sodium tetrakis-3,5-bis(trifluoromethyl)phenylborate (NaBArF). The cationic iridium complexes showed high reactivity and excellent enantioselectivity in the asymmetric hydrogenation of 1-methylene-tetrahydro-benzo[d]azepin-2-ones (up to 99% yield and up to 99% ee). A key intermediate of the anti-obesity drug lorcaserin could be efficiently synthesized using this protocol.

Lorcaserin Administration has Pro-Ejaculatory Effects in Rats via 5-HT2C Receptors Activation: A Putative Pharmacologic Strategy to Delayed Ejaculation?

BACKGROUND

Lorcaserin is an anti-obesity drug whose weight loss effect results from 5-hydroxytryptamin (5-HT)_2C receptors activation. The 5-HT_2C receptor was shown to participate in the physiological control of ejaculation, but no data addressing a putative effect of lorcaserin on ejaculation exist.

AIM

To investigate the effects of lorcaserin in different in vitro and in vivo experimental models of ejaculation in rats.

METHODS

Contractile responses to lorcaserin in rat seminal emission organs in vitro (prostatic and epididymal vas deferens, cauda epididymis, and seminal vesicles), analysis of male rat copulatory behavior, and electromyographic recording of bulbospongiosus muscle in anesthetized animals were studied.

MAIN OUTCOME MEASURES

The main outcome measures included in vitro contraction of seminal emission organs and evaluation of the male rat copulatory behavior. The male rat sexual behavior in terms of copulation latency, ejaculation latency, mount and intromission frequency, and ejaculation frequency of sexually experienced adult male rats with a receptive female were also recorded.

RESULTS

Lorcaserin (1.0 nM to 1.0 mM) had no significant effects on the in vitro contractility of seminal emission organs smooth muscle (cauda epididymis, vas deferens, and seminal vesicles). On the other hand, lorcaserin administration (0.3-1.0 mg/kg, intravenous) induced ejaculation in anesthetized rats, which was prevented by the 5-HT_2C-selective antagonist SB 242084 (0.1 and 0.3 mg/kg, intravenous). Single-dose treatment of non-anesthetized male rats with lorcaserin (1.0, 4.0, or 10 mg/kg, per os) induced non-copulating ejaculations in sexually naïve rats. Lorcaserin also had pro-ejaculation effects by decreasing the ejaculation threshold of copulating rats by half. The pro-ejaculatory effects of lorcaserin were reversible as the ejaculation threshold of treated rats recovered after a 1-week washout period.

CLINICAL IMPLICATIONS

Due to its reported clinical safety, repurposing lorcaserin for the treatment of delayed ejaculation may be suggested.

STRENGTHS & LIMITATIONS

The pro-ejaculatory effect of lorcaserin administration and the role of 5-HT_2C were demonstrated in different experimental models of ejaculation in rats. The lack of studies in putative experimental models of delayed ejaculation is a limitation of this study.

CONCLUSION

Our results demonstrate that the clinically approved 5-HT_2C agonist lorcaserin is a strong facilitator of ejaculation in rats. de Almeida Kiguti LR, Pacheco TL, Antunes E, et al. Lorcaserin Administration has Pro-Ejaculatory Effects in Rats via 5-HT2C Receptors Activation: A Putative Pharmacologic Strategy to Delayed Ejaculation? J Sex Med 2020;17:1060-1071.

Evaluation of Selective 5-HT2C Agonists in Acute Seizure Models

The 5-HT releaser/reuptake inhibitor fenfluramine has been recently reported to provide benefit as an adjunctive treatment for Dravet and Lennox-Gastaut syndromes, two types of severe childhood epilepsy. Despite its enhancement of 5-HT function, many effects of fenfluramine have been demonstrated to be dependent on 5-HT_2C receptor activation, suggesting that 5-HT_2C receptor activation may have an anticonvulsant property. The present study was designed to evaluate fenfluramine and 5-HT agonists of varying 5-HT_2C agonist selectivity, the relatively nonselective mCPP and Ro 60-0175, and the selective 5-HT_2C agonists lorcaserin and CP-809101 across a variety of acute seizure tests conducted in adult rats and mice, which have been instrumental in identifying the majority of clinically efficacious antiepileptic drugs. Tests included the maximal electroshock seizure (MES), MES threshold, and 6 Hz electrical convulsive seizure models and the chemoconvulsant pentylenetetrazole test. The effect of mCPP, lorcaserin, and CP-809101 against electrically evoked seizures in amygdala kindled rats was also investigated. Overall, at doses known to interact with 5-HT_2CR, there was no clear class-related effect of these agonists in any test. The only notable antiseizure effect of fenfluramine was inhibition of MES-induced tonic seizures in the rat. The current preclinical studies using the classical acute seizure tests and an amygdala kindling model do not identify a reliable antiseizure effect of fenfluramine, an agent now used in the treatment of human epilepsies, including Dravet syndrome and Lennox-Gastaut syndrome. Given the nature of these epilepsies, early life and/or genetic models may have better construct validity and be more appropriate for further study.

Current Options for the Pharmacotherapy of Obesity

650 millions of adults are obese worldwide - in the US alone, forty percent of the adults are obese. Although the obesity pandemic is constantly expanding at very high costs for health care systems, the currently available options of pharmacotherapy for obesity are rather limited. Despite intensive research efforts, the vast majority of the anti-obesity drugs developed up to now have a rather limited efficacy and/or safety profile. In the last fifty years, various drugs reached advanced states of clinical development but were either never marketed or were initially approved but withdrawn later due to safety issues. However, the understanding of the pathophysiology of obesity has been steadily improving and new, promising drugs targeting various selective obesityassociated and energy-homeostasis-related pathways are now available. When lifestyle changes alone fail to combat, then additional pharmacotherapy with an acceptable efficacy and safety profile could provide a useful therapeutic option.

Morus alba, a Medicinal Plant for Appetite Suppression and Weight Loss

The prevalence of obesity is expanding rapidly worldwide, making the disease a global burden with limited treatment options. The current obesity drug development trends suggest the possibility of reducing weight and reverse metabolic disturbances of obesity by controlling appetite. In this study, we screened more than 8000 plants from our plant library for the cannabinoid (CB₁) receptor antagonists and identified Morus alba as a lead medicinal plant. Kuwanon G and Albanin G were isolated and identified from root-barks of Morus alba with 92% and 96% CB₁ receptor ligand binding inhibitory activity, respectively. The bioflavonoid standardized extract was tested in the acute food intake study in rats at oral doses of 250 and 500 mg/kg for its appetite suppression activity. Diet-induced obesity in the C57BL/6J mice was used to evaluate the long-term food intake reduction activity and effect on the weight loss administered orally at 250 and 500 mg/kg for 7 weeks. Statistically significant and dose-dependent reduction in food intake was observed in both acute and long-term studies for the extract. Food intake reductions of 58.6% and 44.8% at 250 mg/kg and 50.1% and 44.3% at 500 mg/kg were observed at 1 and 2 h postfood provision, respectively. A 20% reduction in daily calorie intake was observed in the long-term study. Obese mice treated with the high dose of Morus root-bark extract showed 10.4 g (22.5%) and 7.1 g (16.5%) loss in body weight compared with the vehicle-treated obese animals (at week 7) and baseline, respectively. Statistically significant reductions in biochemical markers and visceral fat deposit were also observed. These results demonstrated that Morus alba extracts enriched in Kuwanon G, and Albanin G could be used alone to control appetite, manage body weight, and improve metabolic syndromes.

Effect of lorcaserin in different age groups: a post hoc analysis of patients from the BLOOM, BLOSSOM and BLOOM-DM studies

INTRODUCTION

The elderly population is projected to be the fastest growing group of individuals with obesity group in the United States. As such, there is merit in examining factors that contribute to healthy aging and weight management. The effects of newer weight loss medications approved after 2013 have been studied but are not often assessed specifically in older persons.

METHODS

This post hoc analysis evaluated the magnitude of weight loss in adults across age quartiles with lorcaserin, a serotonin (5-HT) 2C receptor agonist indicated as an adjunct to a reduced-caloric diet and increased physical activity for chronic weight management. Data from three lorcaserin pivotal phase 3 studies were used in this analysis. Data for patients with overweight/obesity without type 2 diabetes (T2D; BLOOM/BLOSSOM; body mass index [BMI] 27.0-29.9 kg/m2 and ≥1 comorbidity or BMI 30.0-45.0 kg/m2) and patients with overweight/obesity with T2D (BLOOM-DM; BMI 27.0-45.0 kg/m2) were used. Patients were randomized to receive lorcaserin 10 mg twice daily or placebo in addition to diet and exercise for 52 weeks. Age quartiles between the studies differed as the T2D population was on average, 9 years older.

RESULTS

This analysis shows that lorcaserin was associated with improved weight loss relative to placebo regardless of age. Importantly, these results were consistent for patients with and without T2D. Interestingly, the magnitude of weight loss for lorcaserin appeared to increase with increasing age. In patients without T2D, odds of achieving ≥5% and ≥10% reduction in body weight at 52 weeks were significantly higher for patients >36 years. Lorcaserin was well tolerated in all patients across all quartiles including the oldest quartile.

CONCLUSIONS

In summary, this post hoc analysis demonstrates that lorcaserin treatment in patients with and without T2D was safe and effective at reducing weight across all age groups analysed. Weight loss appeared to be greater for older patients; additional analyses are warranted to confirm these findings and to better understand the factors for improved weight loss.

Effect of ASP2205 fumarate, a novel 5-HT2C receptor agonist, on urethral closure function in rats

The pharmacological profile of ASP2205 fumarate (ASP2205), a novel 5-HT_2C receptor agonist, was evaluated in vitro and in vivo. ASP2205 showed potent and selective agonistic activity for the human 5-HT_2C receptor, with an EC₅₀ of 0.85 nM in the intracellular Ca²⁺ mobilization assay. Rat 5-HT_2C receptor was also activated by ASP2205 with an EC₅₀ of 2.5 nM. Intraduodenal administration (i.d.) of ASP2205 (0.1-1 mg/kg) significantly elevated the leak point pressure (LPP) in anesthetized rats in a dose-dependent manner. This ASP2205 (0.3 mg/kg i.d.)-induced LPP elevation was inhibited by SB242084 (0.3 mg/kg i.v.), a selective 5-HT_2C receptor antagonist. Urethral closure responses induced by intravesical pressure loading in rats were enhanced by ASP2205 (0.3 mg/kg i.v.), which was abolished by pretreatment with SB242084 (0.3 mg/kg i.v.) and bilateral transection of the pudendal nerve. In contrast, ASP2205 (0.3 mg/kg i.v.) did not change the resting urethral pressure in rats. These results indicate that ASP2205 can enhance the pudendal nerve-mediated urethral closure reflex via the 5-HT_2C receptor, resulting in the prevention of involuntary urine loss.

5-HT2 receptor binding, functional activity and selectivity in N-benzyltryptamines

The last fifteen years have seen the emergence and overflow into the drug scene of "superpotent" N-benzylated phenethylamines belonging to the "NBOMe" series, accompanied by numerous research articles. Although N-benzyl substitution of 5-methoxytryptamine is known to increase its affinity and potency at 5-HT2 receptors associated with psychedelic activity, N-benzylated tryptamines have been studied much less than their phenethylamine analogs. To further our knowledge of the activity of N-benzyltryptamines, we have synthesized a family of tryptamine derivatives and, for comparison, a few 5-methoxytryptamine analogs with many different substitution patterns on the benzyl moiety, and subjected them to in vitro affinity and functional activity assays vs. the human 5-HT2 receptor subtypes. In the binding (radioligand displacement) studies some of these compounds exhibited only modest selectivity for either 5-HT2A or 5-HT2C receptors suggesting that a few of them, with affinities in the 10-100 nanomolar range for 5-HT2A receptors, might presumably be psychedelic. Unexpectedly, their functional (calcium mobilization) assays reflected very different trends. All of these compounds proved to be 5-HT2C receptor full agonists while most of them showed low efficacy at the 5-HT2A subtype. Furthermore, several showed moderate-to-strong preferences for activation of the 5-HT2C subtype at nanomolar concentrations. Thus, although some N-benzyltryptamines might be abuse-liable, others might represent new leads for the development of therapeutics for weight loss, erectile dysfunction, drug abuse, or schizophrenia.

A new enantioselective synthesis of antiobesity drug lorcaserin

A simple and efficient enantioselective synthesis of anti-obesity drug lorcaerin starting from easily accessible 3-chlorostyrene oxide has been described for the first time employing hydrolytic kinetic resolution as a source of chirality.

Pimavanserin and Lorcaserin Attenuate Measures of Binge Eating in Male Sprague-Dawley Rats

Binge eating disorder (BED) is characterized by dysregulated feeding and reward-related processes, and treatment is often challenged by limited therapeutic options. The serotonin (5-HT) 5-HT_2A receptor (5-HT_2AR) and 5-HT_2CR are implicated in both feeding-related and reward-related behaviors and are thus poised to regulate BED-related behaviors. The purpose of this study was to assess the efficacy of the FDA-approved medications pimavanserin, a 5-HT_2AR antagonist/inverse agonist, and lorcaserin, a 5-HT_2CR agonist, in a rodent model of binge eating. The effects of pimavanserin (0.3–3.0 mg/kg), lorcaserin (0.25–1.0 mg/kg), and the lowest effective dose of pimavanserin (0.3 mg/kg) plus lorcaserin (1.0 mg/kg) were tested in a high-fat food (HFF) intermittent access binge eating model in adult male Sprague-Dawley rats (n = 64). We assessed three measures related to binge eating – binge episode occurrence, binge intake, and weight gain associated with HFF access. Pimavanserin decreased binge intake and weight gain associated with HFF access, but did not prevent binge episode occurrence. Lorcaserin decreased binge intake, but did not prevent binge episode occurrence or weight gain associated with HFF access. Combined pimavanserin plus lorcaserin prevented binge episode occurrence in addition to decreasing binge intake and weight gain associated with HFF access. These preclinical findings in male rats suggest that pimavanserin and lorcaserin may be effective in treating patients with BED. Our studies further indicate that administration of one or both drugs may be more effective in certain sub-populations of patients with BED because of the unique profile each treatment elicits. These data support future assessment in clinical populations with BED.

Substitution-Controlled Selective Formation of Hexahydrobenz[ e]isoindoles and 3-Benzazepines via In(OTf)3-Catalyzed Tandem Annulations

A dramatic N-substituent controlled tandem annulation of 2-(2-(2-bromoethyl)phenyl)-1-sulfonylaziridines with 1,3-dicarbonyl compounds has been developed. When the N-substituent was a 4-methylbenzenesulfonyl group (Ts), sequential ring opening of aziridines, nucleophilic substitution, and lactamization took place to provide a series of hexahydrobenz[ e]isoindole compounds in good yields with good diastereoselectivities. By contrast, 3-benzazepine compounds were afforded in good yields via ring opening of aziridines and nucleophilic substitution when the N-substituent was the 4-nitrobenzenesulfonyl group (Ns).

Challenging obesity, diabetes, and addiction: the potential of lorcaserin extended release

Obesity is a global epidemic that is a leading cause of preventable death. In addition to lifestyle modification, there are numerous obesity treatments for clinicians to consider, including medications. Lorcaserin immediate release/extended release (IR/XR) is a US Food and Drug Administration approved medication for overweight and obese patients to be used with lifestyle modifications. Lorcaserin is thought to reduce weight by targeting the serotonin (5HT2c) system to induce satiety. Lorcaserin IR has been shown to be effective in reducing weight in overweight (body mass index [BMI] > 27 kg/m2) and obese (BMI > 30 kg/m2) participants in three large Phase III trials. In addition, lorcaserin has been shown to reduce post-cessation weight gain and improved smoking cessation in a randomized placebo-controlled trial. A recent meta-analysis suggested in overweight diabetic patients lorcaserin may be added to first-line oral hypoglycemic medications to enhance reduction in glycated hemoglobin. Lorcaserin is generally well tolerated with the most common side effect being headache, which is typically self-limiting. Lorcaserin XR (once daily) was recently approved and has been shown to be bioequivalent to lorcaserin IR (twice daily) in a pivotal study. Lorcaserin XRs, main advantage over the IR formulation is the once daily dosing regimen, which likely would lead to improved adherence and thus improved clinical effectiveness. The present review will evaluate the lorcaserin clinical studies (obesity, diabetes, and addiction), XR bioequivalence studies, pharmacogenomics of the serotonin (5HT2c) system, and adherence data in once daily versus twice daily medications.

Idalopirdine, a selective 5-HT6 receptor antagonist, reduces food intake and body weight in a model of excessive eating

Obesity, from early childhood onwards, is a common societal problem. The overconsumption of sweet, salty and high-fat products are the main factors that cause excessive weight gain. It is therefore necessary to search for new drugs that affect satiety centers and reduce the sense of hunger and caloric intake. It has been suggested that the blockade of 5-HT₆ receptors may reduce food intake, and since idalopirdine is a clinically tested, selective 5HT₆ receptor antagonist, it was chosen to be examined in animal models of obesity. The activity of idalopirdine was measured in the rat model of excessive eating. Animals were on a high caloric diet that consisted of milk chocolate with nuts, cheese, salted peanuts and condensed milk. During a four-week experiment, the rats had constant access to standard feed and water ad libitum. Idalopirdine was administered intraperitoneally at a dose 5 mg/kg b.w./day. To establish whether idalopirdine would effectively suppress the rebound hyperphagia that accompanies refeeding, it was administered after a 20 h food deprivation period. Pica behavior was evaluated after the administration of idalopirdine to confirm that the suppression of food intake was not caused by visceral illness. The effect of the four-week treatment with idalopirdine on the amount of peritoneal adipose tissue, and on lipid and carbohydrate profiles in rats was also examined. The statistical significance was calculated using the one-way ANOVA post-hoc Tukey Multiple Comparison Test or the two-way ANOVA post-hoc Bonferroni Multiple Comparison Test. Idalopirdine significantly reduced caloric intake and prevented the development of obesity in tested animals. Rats, that received idalopirdine, had a smaller amount of adipose tissue in the peritoneum as well as lower glucose, triglyceride and cholesterol levels in comparison to the control group. Moreover, an anorectic action was not caused by abnormalities of the gastrointestinal tract, such as nausea. The obtained results indicate that idalopirdine reduces caloric intake and could be considered for further tests as a potential treatment of obesity.

Understanding and Improving the Activity of Flavin-Dependent Halogenases via Random and Targeted Mutagenesis

Flavin-dependent halogenases (FDHs) catalyze the halogenation of organic substrates by coordinating reactions of reduced flavin, molecular oxygen, and chloride. Targeted and random mutagenesis of these enzymes have been used to both understand and alter their reactivity. These studies have led to insights into residues essential for catalysis and FDH variants with improved stability, expanded substrate scope, and altered site selectivity. Mutations throughout FDH structures have contributed to all of these advances. More recent studies have sought to rationalize the impact of these mutations on FDH function and to identify new FDHs to deepen our understanding of this enzyme class and to expand their utility for biocatalytic applications.

Crystal structure of the human 5-HT1B serotonin receptor bound to an inverse agonist

5-hydroxytryptamine (5-HT, also known as serotonin) regulates many physiological processes through the 5-HT receptor family. Here we report the crystal structure of 5-HT1B subtype receptor (5-HT1BR) bound to the psychotropic serotonin receptor inverse agonist methiothepin (MT). Crystallization was facilitated by replacing ICL3 with a novel optimized variant of BRIL (OB1) that enhances the formation of intermolecular polar interactions, making OB1 a potential useful tool for structural studies of membrane proteins. Unlike the agonist ergotamine (ERG), MT occupies only the conserved orthosteric binding pocket, explaining the wide spectrum effect of MT on serotonin receptors. Compared with ERG, MT shifts toward TM6 and sterically pushes residues W3276.48, F3306.50 and F3316.51 from inside the orthosteric binding pocket, leading to an outward movement of the extracellular end and a corresponding inward shift of the intracellular end of TM6, a feature shared by other reported inactive G protein-coupled receptor (GPCR) structures. Together with the previous agonist-bound serotonin receptor structures, the inverse agonist-bound 5-HT1BR structure identifies a basis for the ligand-mediated switch of 5-HT1BR activity and provides a structural understanding of the inactivation mechanism of 5-HT1BR and some other class A GPCRs, characterized by ligand-induced outward movement of the extracellular end of TM6 that is coupled with inward movement of the cytoplasmic end of this helix.

Lorcaserin for Smoking Cessation and Associated Weight Gain: A Randomized 12-Week Clinical Trial

Introduction

Lorcaserin is a selective serotonin 2C receptor agonist approved by the Food and Drug Administration for chronic weight management. Preclinical data suggest that it may also be effective in smoking cessation through modulation of the dopaminergic reward system.

Methods

This was a 12-week, randomized, double-blind, placebo-controlled trial conducted in 30 centers in the United States. Six hundred three adult smokers with a Body Mass Index of 18.5-35 kg/m2, averaging at least 10 cigarettes/day with no period of abstinence >3 months for the past year were randomized to lorcaserin 10 mg once daily (QD), 10 mg twice daily (BID) or placebo; all received standardized smoking cessation counseling weekly. The target quit date was day 15. The primary endpoint was the exhaled carbon monoxide confirmed Continuous Abstinence Rate for weeks 9-12 (month 3).

Results

Continuous Abstinence Rates for month 3 were 5.6%, 8.7%, and 15.3% for the placebo, QD and BID groups, respectively (BID vs. placebo odds ratio 3.02, 95% confidence interval 1.47, 6.22, p = .0027. Change in weight at week 12 (randomized population) was -0.01, -0.35 and -0.98 kg, respectively (p = .0004, BID vs. placebo), and +0.73, +0.76, and -0.41 kg in participants achieving month 3 continuous abstinence. The most frequent adverse events were headache, nausea, constipation, and fatigue.

Conclusions

Lorcaserin with counseling was associated with dose-related increases in smoking cessation and prevention of associated weight gain over a 3-month period. Further investigation of lorcaserin in smoking cessation is warranted. Trial Registration: ClinicalTrials.gov. Identifier: NCT02044874.

Implications

This randomized, controlled trial demonstrated that lorcaserin used in conjunction with standard cessation counseling was associated with dose-related increases in smoking cessation and prevention of associated weight gain. To our knowledge, this is the first demonstration in humans of a potential role of 5-HT2C agonism in the modulation of central neurological circuits involved with reward.

Development and optimization of a new synthetic process for lorcaserin

A two-step process to synthesize racemic lorcaserin was developed from 2-(4-chlorophenyl)ethanol via formation of bromide or tosylate derivatives. These derivatives were reacted with allylamine in neat conditions to provide pure N-(4-chlorophenethyl)allylammonium chloride. This compound was cyclized in neat conditions using aluminum or zinc chloride to give racemic lorcaserin. After resolution of enantiomers, the wrong enantiomer was racemized and recycled to give new R-lorcaserin.